While for years I have been exclusively playing my home campaign with friends, I am now more and more playing D&D at a local role-playing club. The campaigns there are frequently shorter, and so I get to roll a new character more often. And then the question is often what classes in 5th edition Dungeons & Dragons are "good" or "the best". If you know me, you can guess that my answer to that question is "it depends". And I would like to use this post to explain why there isn't a simpler answer, and what exactly it depends on.

If you compare Dungeons & Dragons with a MMORPG, like World of Warcraft, you will see that in spite of many similarities, there are also some fundamental differences. World of Warcraft has a very well defined style and genre. You know what the challenges are that your character has to overcome, and can optimize accordingly. Dungeons & Dragons is very different in that, because you can play adventures of different styles and even genres. You can do high fantasy, low fantasy, dark fantasy, and even more exotic stuff like steampunk within the same rules system. And an adventure could be a dungeon crawl, or it could be a city adventure with a murder investigation. So that is the first thing you need to know if you want to make a good character: What kind of a campaign are you joining? A bard with lots of social skills might be great in a city adventure, but would he still be that great in a dungeon crawl? On the other side the half-orc barbarian is maybe more suited for that dungeon crawl than for that murder investigation.

Usually a DM will give some hints on what his campaign is about, so you can make that choice with some forethought. Unfortunately other decisions of the DM are harder to foresee, and play a huge role on class balance. The most important here might be the flow of encounters and occasions for resting. It helps to think of a character having two states: A "high" state, where he is freshly rested and has access to all of his resources that have some sort of a daily limit, and a "low" state where he has used up all these resources. Let's have a look for example at the fighter compared to the barbarian: For the basic "champion" fighter, the difference between the high state and the low state isn't all that much. Even if you have used your second wind and action surge you are still turning out a steady stream of damage and have good defenses. And both of these only require a short rest to recover. For the barbarian it makes a much bigger difference whether he still has rages or not. While the rage state can last a whole combat encounter, the barbarian only gets a limited number of rages per long rest. And rage affects both your damage output and your defenses. So now imagine two different DMs: One who puts the group in a situation where (as the Dungeon Master's Guide suggests) you have 6 to 8 encounters per adventuring day, with two short rests. And another DM who is far more generous with resting opportunities and ends up having only 2 or 3 encounters between long rests. It is easy to see how the fighter would do better with the first DM, while the barbarian would do better with the second one. And usually you don't know the DM's playing style in advance.

As a corollary to that you can also think about how "epic" each of the encounters are. Fewer encounters frequently means harder encounters against big boss mobs. More encounters can be lots of small fights. Again that makes a difference to the efficiency of different classes. That raging half-orc barbarian with great weapons mastery would be a great choice against a big monster with lots of hit points. Against a group of kobolds dealing single huge blows would be a lot less effective, and maybe a monk doing multiple, smaller attacks would do better.

The environment also plays a role: I've been in combat situations with a group with mostly melee attackers, where the number of people able to hit an enemy was limited. If you play a dungeon with lots of fights in 10 foot wide corridors, a ranged attacker would have an easier time to consistently find a target. On an open field not only is there less of an advantage of attacking ranged, but with D&D lacking "taunt" mechanics a "glass cannon" type of character might end up dead quickly if the DM decides to just circumvent the tanks and have the monsters attack the back row.

Related to the environment is the type of challenge the players are facing. Not every problem can be solved with a greatsword, although I know players who try exactly that. In the "dungeon of a thousand traps" a character like a rogue will have a lot of opportunities to shine. There are adventures where combat skills are all that matter, while others require a lot of skill checks. Unfortunately sometimes skill checks are optional, and if the group works on a "the first one to speak effectively decides the group action" basis the guy wanting to attack everything is likely to overrule the more cautious characters wanting to use alternative solutions.

The final element I would like to mention is the level of the characters. Different classes gain different abilities at different levels. That frequently leads to a situation where a given ability is very powerful at the level where you receive it, but then becomes less and less powerful in comparison with rising levels. Some examples are: The sleep spell of bards and wizards, which is extremely powerful at level 1, but doesn't scale very well and becomes much weaker over the following levels. Or the moon druid turning into a CR 1 monster at level 2, which at that level is quite strong, but being a lot less strong in comparison at level 5. Of course that is also related to the problem mentioned above on how likely you are to run out of resources: Doing 6 to 8 encounters at level 1, where a wizard has 2 spell slots is a lot different from doing 6 to 8 encounters at level 10, where he has 15 spell slots. Wizard would be a typical class that grows comparatively more powerful to other classes with higher levels, because he gets both more spells and better spells (the "quadratic wizard" balance problem), while other classes don't grow in power that fast.

Ultimately which character is best for you also not only depends on the circumstances, but also on your own requirements. How happy would you be playing a support class, whose successes are more about saving another player than being the one who kills the dragon? How happy would you be playing something chaotic and unreliable, like a wild magic sorcerer? Do you choose your race because it gives the best bonuses to your stats and best traits, or do you enjoy role-playing a particular race? How important is optimization for you in general?

Between different campaign environments, different DM styles, and different player styles, every single class in 5th edition Dungeons & Dragons is viable for something. There are a few that are generally reputed to be weak, like the beast master ranger, but even those might be good in the right circumstances for the right player. If you have the opportunity to experiment with shorter campaigns, use it to experiment!

It's all relative. I've played with people that didn't care about being useful in 95% of the game, as long as they could cast a fireball that completely destroyed that 1-in-10 encounter that would eventually get thrown the PC's way. And then there are people who like to roleplay that charming but fairly combat-inefficient rogue-type PC, that picks pockets, chats up barmaids and tries to start a dialogue with the highway bandits that just jumped the caravan.

Al long as you get a balance of all player types in the group then it should be smooth sailing for everyone involved in the campaign.

Yes. By the way, the rogue is actually more efficient in 5E than in previous editions. The conditions necessary for him to do additional sneak attack damage have been lowered to a point where he should be able to do it every round. And there is a good chance to hide and do ranged attacks with advantage.

Seeing as I haven't played since 3rd edition, your mention about the DM fudging(?) placements where the Tanks and other classes are concerned has me wondering if the rules have foregone the responsibility of the party members to decide where they are located on the map for any given location? From what I gather from the PHB for 5E, it seems as if it's written from a thematic approach without the need for maps and miniatures. How does 5E retain immersion elements if that's the case?

I'm playing 5E with a map and miniatures. I know it can be played in "theatre of the mind" mode without any visual aids, but I never played it that way.

While maps do help, 5E is still missing a tanking system. In 4E every tank class had a "mark" power, which more or less forced a monster to hit the tank. In 5E only the paladin has a spell to do something similar, but of course he doesn't have enough spell slots to cast that on every monster he hits, and then the monster still has a saving throw. If the fight happens in a 10' dungeon corridor, two tanks can block the way. But in a bigger room or outside, the monsters can just walk around the tank and attack the characters in the back. Even if in contact with an enemy, you can walk around him without taking opportunity attacks, as long as you don't leave his zone of control.

The sentinel feat provides a number of benefits regarding making a tanks opportunity attacks both more frequent and more meaningful.

Fighters of the battle master "spec" can take "goading strike" with makes it disadvantageous for the target to attack targets other then the fighter. Or "trip attack" which will knock the target prone, so they'd need to spend their movement getting up rather then moving to attack someone else